Dimpling: The Final Dimpling: The Final FrontierFrontier

It’s not just for golf balls and It’s not just for golf balls and grandmothers anymore!grandmothers anymore!Student: Jason BurbeyStudent: Jason Burbey

Faculty Advisor: Professor Eric StachFaculty Advisor: Professor Eric Stach

OutlineOutline

BackgroundBackground ObjectiveObjective Sample Preparation/CharacterizationSample Preparation/Characterization Sample Prep. InstrumentsSample Prep. Instruments Work CompletedWork Completed Future WorkFuture Work AcknowledgementsAcknowledgements QuestionsQuestions

BackgroundBackground Professor Ravi Professor Ravi

ChandranChandran• University of UtahUniversity of Utah

Laminated Steel and Laminated Steel and BrassBrass• Repeated cold rollingRepeated cold rolling• Continuation of Continuation of

previous studyprevious study Evaluated Mechanical Evaluated Mechanical

PropertiesProperties• Inverse relationship Inverse relationship

between yield strength between yield strength and bilayer thicknessand bilayer thickness

• Yield strengths as high Yield strengths as high as 850 MPa as 850 MPa

Why?Why?• Microstructural Microstructural

characterization neededcharacterization neededRavichandran, K. “Nanoscale Steel-Brass Multilayer Laminates Made By Cold Rolling: Microstructure and Tensile Properties.” Scripta Materialia Vol 42: 949,951

ObjectiveObjective

Microstructural Characterization of Microstructural Characterization of laminateslaminates• Bright Field Images in TEMBright Field Images in TEM

Features of interest:Features of interest:• Bilayer thicknessBilayer thickness• Interlamellar structureInterlamellar structure• Dislocation density and distributionDislocation density and distribution

Sample Sample Preparation/CharacterizationPreparation/Characterization

Dimple specimens to 10-15umDimple specimens to 10-15um

Ion Mill to produce very small hole in Ion Mill to produce very small hole in specimenspecimen• Electron TransparentElectron Transparent

Take bright-field images of specimen Take bright-field images of specimen using TEMusing TEM

The DimplerThe Dimpler

Model 2000 Model 2000 Sample Prep Sample Prep SystemSystem

Diamond Slurries Diamond Slurries and pastesand pastes• 6,3,1, .25 micron6,3,1, .25 micron

The Ion MillThe Ion Mill

Gatan Model 600 Gatan Model 600 Duo-MillDuo-Mill

ArAr++ ions directed at ions directed at specimen from specimen from both sides at a set both sides at a set angleangle

Fairly time Fairly time consumingconsuming

Transmission Electron MicroscopeTransmission Electron Microscope

JEOL Model 2000FXJEOL Model 2000FX Uses an Ultra High Uses an Ultra High

Vacuum (UHV)Vacuum (UHV)• 1010^-9 ^-9 -10-10^-11 ^-11 atmatm

Capable of high Capable of high resolution images resolution images at high at high magnificationsmagnifications• 1,000,000X or 1,000,000X or

higherhigher• Resolution of < 3ÅResolution of < 3Å

Work completedWork completed

Dimpled metallic laminatesDimpled metallic laminates• SS grinding wheelSS grinding wheel

Ion Mill attemptIon Mill attempt

• Micarta grinding WheelMicarta grinding Wheel Dimpled Ta/Si specimensDimpled Ta/Si specimens Dimpled InAs/GaP specimensDimpled InAs/GaP specimens

Metallic Laminates: SS grinding Metallic Laminates: SS grinding WheelWheel

Thicknesses varied from 90-Thicknesses varied from 90-290um290um

Used 3um slurry and Used 3um slurry and dimpled to 20umdimpled to 20um• Not all specimens were Not all specimens were

20um20um• Used optical microscope Used optical microscope

to check thicknessto check thickness• Re-dimpling difficultRe-dimpling difficult

Specimens 10-15um Specimens 10-15um achievedachieved• Ion Mill trialsIon Mill trials• InefficientInefficient

Start Over!Start Over!• Made more specimensMade more specimens• New dimpling progressionNew dimpling progression• Used different wheelUsed different wheel

Dimpling Laminates: Micarta Dimpling Laminates: Micarta Grinding WheelGrinding Wheel

Micarta Wheel is flatter Micarta Wheel is flatter and thicker than the SS and thicker than the SS grinding wheelgrinding wheel

Dimple the whole Dimple the whole specimen surfacespecimen surface• Used 6um slurryUsed 6um slurry• Sped up dimpling progressSped up dimpling progress

Much smoother surfaceMuch smoother surface• Very important for Ion Very important for Ion

MillingMilling Successful specimens Successful specimens

createdcreated• Stopped after 1um slurryStopped after 1um slurry• More scratches observed More scratches observed

with .25um pastewith .25um paste

SS vs. MicartaSS vs. Micarta

1um slurry vs. .25um paste 1um slurry vs. .25um paste w/micarta wheelw/micarta wheel

Ta/Si SpecimensTa/Si Specimens

Checking phase Checking phase transformation of transformation of TaTa

Blue side = SiBlue side = Si Reflective = TaReflective = Ta Use diamond scribe Use diamond scribe

to cleave to cleave specimensspecimens

Sample PrepSample Prep Problem Problem Dimple on Si sideDimple on Si side

• SS grinding wheelSS grinding wheel Specimens thicker Specimens thicker

than laminatesthan laminates• 470-520um470-520um

Same progression Same progression as laminatesas laminates

Same force exerted Same force exerted by grinding armby grinding arm

Destruction of Destruction of specimensspecimens• Force too much Force too much • Si is fragile!Si is fragile!• Would crack at Would crack at

approx. 20umapprox. 20um

Solution for Ta/Si specimensSolution for Ta/Si specimens

Use less force!Use less force! Progressively Progressively

decrease forcedecrease force• Before switching Before switching

slurry/pasteslurry/paste 3 specimens from 3 specimens from

each bulk sample each bulk sample ready for Ion ready for Ion MillingMilling

In/As specimensIn/As specimens

Thicknesses between Thicknesses between 310-320um310-320um

Dimpled on GaP sideDimpled on GaP side• Used SS grinding wheelUsed SS grinding wheel• Same dimpling Same dimpling

progression as Ta/Siprogression as Ta/Si• Like butter!Like butter!• It smells…It smells…

3 specimens ready for 3 specimens ready for Ion MillingIon Milling

Future WorkFuture Work

Ion Mill all of the different specimensIon Mill all of the different specimens

Characterize specimens in TEM with Characterize specimens in TEM with help from Professor Stachhelp from Professor Stach

Publish characterization resultsPublish characterization results

AcknowledgementsAcknowledgements

Dr. KingDr. King Professor StachProfessor Stach Cheryl WallerCheryl Waller Vijay RawatVijay Rawat Rocco Cerchiara from FischioneRocco Cerchiara from Fischione Jan EberleJan Eberle MSE Dept.MSE Dept.

Questions?Questions?